PEER-REVIEWED ARTICLE bioresources

supports the assumption that the driving force is caused by the pressure gradient. During RF/V drying, a steep pressure gradient along with a temperature gradient is developed from the center towards the surface of timber. The pressure gradient helps to quickly drive out wood moisture in both liquid and vapor form. As the pressure approaches and

SOME COMMENTS ON AIR-WOOD TEMPERATURE …

hours. During the last few hours of kiln residence the drying rate became accelerated (B). Figure 1. Air-Wood Temperature Gradient Figure 2 shows the general relationship between air and wood interior temperatures during drying. In every case the air dry bulb temperature increases from ambient to set point at a much faster rate than the wood ...

Bioinspired large-scale aligned ... - PubMed Central (PMC)

Dec 11, 2015· (To illustrate the breakup of the gradient into vertical and horizontal components during freezing, we use in this paper the expression "dual temperature gradients," although the resulting combined temperature gradient is actually singular.

Layer-like fatigue is induced during mechanical pulping ...

The question whether fatigue is induced during mechanical pulping was addressed experimentally. The grinding process was interrupted to image partly ground spruce samples. The grinding was performed at five different feed velocities using two different grindstones.

Temperature gradient - Wikipedia

Clearly, the temperature gradient may change substantially in time, as a result of diurnal or seasonal heating and cooling for instance. This most likely happens during an inversion. For instance, during the day the temperature at ground level may be …

Non-uniform temperature gradients and thermal stresses ...

Non-uniform temperature gradients and thermal stresses on a hollow sphere 199 Figure 3. Temperature distributions in the midplane of the hollow sphere within the sixth cycle, t = 900 +τ s, (λ = 10W/m-K, H = 1 degree and P = 180s). where λis the thermal conductivity, his the heat transfer coefficient, q (T,φ,t)is a moving

Impact of drying-grinding sequence on loblolly pine chips ...

The high amount of energy consumed during the processing of biomass inflates the production cost of bio-fuels and bio-products. This study was therefore carried out to evaluate the influence of drying and grinding sequence on biomass energy consumption and properties (specific grinding energy requirement, specific drying energy requirement, particle size distribution, bulk density, …

AVOIDING THERMAL DAMAGE IN GRINDING

Following the onset of film boiling, the workpiece surface temperature may rise up to 1000°C or even more under certain conditions. The magnitude of this maximum temperature determines the extent of thermal damage. In creep feed grinding, the damage may be so severe that it can be detected by the naked eye.

Mikko Havimo - Data Scientist - Wärtsilä | LinkedIn

Grinding is an energy intensive process for producing mechanical pulp. This paper presents a novel mathematical model for determining heating process during grinding. It is based on Hertz theory on contact mechanics, and assumes that grind stone grits cause a flux of mechanical energy trough wood.

Modeling kinetics-transport interactions during biomass ...

Because of the high grinding energy requirement of raw biomass [5], industrial scale torrefaction will preferably be performed with large (>2mm) particles. In this case, significantly more complex interactions occur. Heat transfer limitations cause a temperature gradient across

Modeling of moisture diffusion and heat transfer during ...

At low temperature, moisture in wood mainly moves by a diffusion process that is driven by a gradient in the moisture content. Fick's second law offers one generalized method to describe the diffusion process [2, 3]. This approach allows the estimation of moisture gradients at any time during heating period.

Tropical Temperatures At The Cretaceous Poles | Science Trends

Dec 06, 2018· Evidence that the polar regions were much warmer during the Cretaceous Period (145-66 million years ago) compared to today has accumulated during the past century with numerous reports of fossil wood, dinosaurs, and other temperature sensitive organisms that lived in the Arctic and Antarctic regions.

Temperature gradient in wood during grinding - ScienceDirect

The wood viscoelasticity converts mechanical energy into heat, causing excessive heating of the wood. An interesting characteristic of the process is the steep temperature gradient in the wood: during grinding, the temperature of the thin surface layer of log rises from ambient to 150 °C in a few seconds, . The modelling of the temperature ...

Cyclic Temperature-Gradient-Driven Moisture Transport in ...

wood stud on the moisture behavior of part 3 of the back wall, consisting of a wood stud, gypsum board and insulation. Since the wall composition is not uniform, we present the results in kg/m2 and not kg/m3. Before presenting the results, we discuss three issues to be considered: (1) wood is a hygroscopic material and will take up water vapor.

Wood Handbook, Chapter 20: Heat Sterilization of Wood

initial wood temperature) of the wood and wood products being sterilized, and the stacking methods used in the heat treatment process. Energy Source Energy is the amount of heat supplied during the heat treat-ment process. Heat-treating chambers typically employ systems that utilize steam, hot air (direct fire), electricity,

Distribution and variation of pressure and temperature in ...

Full Article. Distribution and Variation of Pressure and Temperature in Wood Cross Section during Radio-Frequency Vacuum (RF/V) Drying. HongHai Liu, a Lin Yang, a Yingchun Cai, b Kazuo Hayashi, c and KaiFu Li a, * The pressure and temperature at the same location in the middle cross section of Sugi wood were measured simultaneously during radio …

EFFECT OF HIGH-PRESSURE COOLANT JET ON GRINDING ...

EFFECT OF HIGH-PRESSURE COOLANT JET ON GRINDING TEMPERATURE, CHIP AND SURFACE ROUGHNESS ... grinding zone reduces the temperature gradient and minimises the seizure effect, offering an adequate ... During each test, grinding zone temperature and surface 22 . VOL.1, NO.4, DECEMBER 2006 ISSN 1819-6608 ...

Chapter 10: Air Quality Flashcards | Quizlet

Start studying Chapter 10: Air Quality. Learn vocabulary, terms, and more with flashcards, games, and other study tools. ... an atmospheric condition during which a warm layer of air stalls above a layer of cool air that is closer to the surface of the earth. normal temperature gradient in atmosphere. warm -> cool -> cooler. temperature ...

Effect of Hot Pressing Temperature on the Density Profile ...

Temperature and moisture contents also affect the properties of the cell wall layers and the consequent response of wood under compression (Fortino et al. 2015). Because of the temperature and moisture gradients formed during hot pressing and their relationship to wood softening where the compression stress is applied, a thickness

MOISTURE TRANSPORT IN WOOD - MODEL TO CREATE …

relative humidity- and the temperature variation on the surface layer of the wood should be known. If the risk of rot should be estimated it is necessary to know the moisture distribution during in the wood. A model for moisture distributions is much more sensitive to the internal flow processes than a model

Impact of drying-grinding sequence on loblolly pine chips ...

The high amount of energy consumed during the processing of biomass inflates the production cost of bio-fuels and bio-products. This study was therefore carried out to evaluate the influence of drying and grinding sequence on biomass energy consumption and properties (specific grinding energy requirement, specific drying energy requirement, particle size distribution, bulk density, tap density ...

A mathematical model of the stone groundwood process: Part ...

This paper focuses on developing a model dealing with temperature rise in wood during grinding. The model paves the way for the development of theoretical methods which can be used for reducing ...

Manufacturing Processes Mid-Term Exam | Engineering ...

Temperature gradients within the workpiece during grinding are primarily responsible for residual stresses. By lowering wheel speed and increasing workpiece speed, residual stress usually can be reduced. ... wood, leather and composite material D: Environmentally safe. A B and C. The quality of the surface finish produced by honing can be ...

modeling of coupled moisture and heat transfer during …

8th International IUFRO Wood Drying Conference - 2003 372 Modeling of Coupled Moisture and Heat Transfer During Wood Drying P. Horáček Mendel University of Agriculture and Forestry Brno, Faculty of Forestry and Wood Technology, CZ-61300 Brno, Czech Republic, E-mail: [email protected]

Whether to Thaw Frozen Wood Before Kiln-Drying

4. If there is a large temperature gradient, with the high conductivity of wood, there will be a lot of heat flowing to the interior to melt any ice, so any gradient will quickly become very small and of little consequence. In conventional drying, the temperature gradient is not the controlling process of drying.

Post-Fire Assessment of structural Wood Members

Post-Fire Assessment of structural Wood Members ... elevated temperatures. during thedecay period offire devel­ ... mal properties of wood, a distinct temperature gradient develops in a wood member when it is exposed to fire. Thus, the loss of structural .

Study of the Vertical Distribution of Air Temperature in ...

analysis to 175,200 vertical temperature profiles show that there is a strong influence of the outdoor temperature over the stratification of the indoor air. During warm months, the ceiling and the upper strata get warmer, whereas the cold air accumulates in the lower levels,

modeling of coupled moisture and heat transfer during wood ...

8th International IUFRO Wood Drying Conference - 2003 372 Modeling of Coupled Moisture and Heat Transfer During Wood Drying P. Horáček Mendel University of Agriculture and Forestry Brno, Faculty of Forestry and Wood Technology, CZ-61300 Brno, Czech Republic, E-mail: [email protected]